One of the principal goals of diabetes research is to generate a large and renewable supply of human insulin-producing beta cells for replacement therapy. Another is to understand how replacement or replenishment might be accomplished from endogenous, residual beta cells. One attractive and tractable approach is the induction of human beta cell replication, so that mature, differentiated human beta cells derived from endogenous sources, from cadaver pancreatic islets, or from the other sources (such as various types of stem cells or reprogrammed cells), might be expanded to numbers capable of treating large numbers of patients with diabetes. Whereas conventional dogma and widespread experience has suggested that adult human beta cells are terminally differentiated and cannot replicate, the investigators in this application have recently shown that this is not completely true. By manipulating cell cycle control, specifically the G1/S control checkpoint of the cell cycle, this group has shown that: a) human beta cells can be induced to replicate rapidly and still retain their differentiated, functional phenotype: and, b) that many direct and indirect, upstream options for human beta cell cycle activation exist. The goals of this application are to assemble a group of senior scientists who focus on all aspects of human beta cell biology and therapy, to facilitate and expedite human beta cell replication, differentiation and replacement strategies, and to share this expertise with the other members of the Beta Cell Biology Consortium (BCBC). The Specific Aims are: 1) To Fully Define The Normal Physiology, Mechanisms of Action, Therapeutic Efficacy and Safety of G1/S Cell Cycle Molecules In The Human Beta Cell. 2) To Explore the Regulatory Pathways Upstream Of The G1/S Checkpoint To Define Beta-Cell Specific Pathways To Activate Proliferation in Human Beta Cells. 3) To Share Knowledge, Data, Reagents, Animals, Technologies, and Techniques with Other BCBC Investigators. Data already in hand indicates that there are many novel ways to induce human beta cell replication, and that additional focus and refinement should help transform these approaches from laboratory bench research to human diabetes therapy.